An even flow of the gas phase fluid in hoppers is often desirable for the efficient operation of equipment such as bag house filter systems. Conventionally, controlling the flow is based primarily on the use of scale models and experience. As a result, in conventional systems the flow is very non-uniform.
Typically, the hoppers are fed from a central header. The flow enters the hopper from one side and is then directed upwardly. Guide vanes are often installed in the hopper to direct the flow. Such guide vanes are typically oriented at right angles to the incoming flow direction. In many cases, the guide vanes are ineffective in promoting an even flow. In the case of bag house filter systems, this uneven flow distribution results in regions of high upward or horizontal velocity flow impinging on the bags. This high velocity flow causes high wear and premature failure of the bags. The uneven flow distribution results in uneven loading on the filter bags and premature clogging of the bags.
Using Computational Fluid Dynamics, a mathematical modeling procedure, fluid flow in the hopper system can be computed. The mathematical procedure used in the CFD process can consist of Finite Element or Finite Volume methods, as well as other methods known to fluids analysts. The use of CFD allows the analyst to produce numerical and visual representations of the fluid flow. Using this method, apparatus in accordance with the present invention can be custom-tuned to the hopper system and operating conditions. This tuning entails shaping an inlet guide to direct flow to the optimal spot on a diffuser and adjusting the placement, open area and angle of the diffuser. Pictorial representations of the fluid flow field, as well as numerical analysis of the flow field velocities, are used to evaluate the suitability of the flow patterns.
In accordance with the present invention, particulate-laden gas is directed into the hopper from one side thereof through an inlet guide. The inlet guide directs the flow against the bottom, upstream side of a porous diffuser that spans the hopper below a multiplicity of filter bags disposed at a higher position in the system. Passages through the diffuser are dimensioned and configured to serve as an array of nozzles so as to cause the gas to experience a pressure-drop as it passes through the diffuser, thereby forcing gas from the inlet guide to be evenly distributed across the upstream side of the diffuser. The gas thus passes to the bags in a smoother, more evenly distributed manner than in prior art systems, improving efficiency and reducing premature equipment wear.